Variable aperture antenna system



Aug. 16, 1966 c. FINK 3,267,472

VARIABLE APERTURE ANTENNA SYSTEM Filed July 20, 1960 4 Sheets-Sheet 1 ya 2 X'JZ ax 71 7 g! 73% 55 i7 5 5 a;

INVENTOR ORNEYS Aug. 16, 1966 c. FINK 3,267,472

VARIABLE APERTURE ANTENNA SYSTEM Filed July 20, 1960 4 sheets-sheet 2 a2 INVENTOR W ATTORNEYS Aug. 16, 1966 c. FINK 3,267,472

VARIABLE APERTURE ANTENNA SYSTEM Filed July 20, 1960 4 Sheets-Sheet s CarZeas 227g}; /7/ 5/ M6 49. Ma i);

ATTORNEYS Aug. 16, 1966 c. FINK 3,267,472

VARIABLE APERTURE ANTENNA SYSTEM Filed July 20, 1960 4 Sheets-Sheet 4 4 XI Adm/far A W INV E NTOR [Mr/es Fax/Z;

BY Q AJ M ATTORNEYS United States Patent Ofiice Patented August 16, 1966 3,267,472 VARIABLE APERTURE ANTENNA SYSTEM Charles Fink, Silver Spring, Md., assignor to Litton Systems, Incorporated, College Park, Md. Filed July 20, 1960, Sex. No. 44,174 19 Claims. (Cl. 343100) This invention generally relates to improvements in variable aperture antenna arrays, and more particularly to multiple application antenna array systems that are adjustable for providing a wide variety of different beam shapes or patterns and are adapted for efiicient operation over a wide bandwidth of frequencies.

It is, accordingly, a primary object of the invention to provide a versatile antenna system of minimum complexity for multi-purpose use in such applications as radar, communication, and surveillance.

For such diverse purposes as target detection, height finding and locating, tracking and the like, it is necessary to provide differently shaped antenna beams that are best adapted to determine the different information desired. For example, in determining the azimuth position of a target accurately, a fan-shaped beam that is thin in azimuth but broad in elevation is most suitable, whereas for locating the height or elevation of a target, the beam should also be fan-shaped but rather be thin in elevation and broad in azimuth. Although these differing beam shapes may be provided by a series of differently constructed antennae, it is highly desirable to provide a single multi-function antenna system that may be adjusted as required to produce these different beam shapes and patterns.

In general, the pattern characteristics of any antenna is a function of the amplitude and phase of the current distribution in the antenna aperture. This aperture may consist of a reflecting or focusing area such as a parabolic surface or it may consist of a series of spaced antenna elements known as an antenna array. In the former, the aperture may be varied by physically changing the shape of the reflector or focusing area whereas in the latter, it is known to vary the beam pattern by. changing the amplitude relationship and/or phase relationship of the signals energizing the different antenna units of the array.

More specifically considering the characteristics of an antenna array with which the present invention is most concerned, the overall beam pattern being produced by the array is determined by a vector summation of the energy being radiated or received by each of the antenna elements in the array. In other words, by summing the spatial contributions of the individual antenna elements, the overall beam pattern is obtained. With this in mind, it becomes evident that the beam pattern being produced by thearray may be varied by changing the amplitude and/or phase relationship of the energy being fed to the individual elements. Furthermore, it is known that if the amplitude and/or phase distribution of the signals supplied to the various elements may be accurately varied, then the resulting beam pattern can be precisely controlled and a variety of pattern shapes can be synthesized to provide a precisely controllable variable aperture antenna.

However, although these characteristics of antenna arrays have been generally recognized by antenna designers, the prior art has experienced considerable difficulty in controllably varying the amplitude distribution of the energy among the various antenna elements without also effecting the phase distribution in a controllable manner, since attenuator devices that have been employed for this purpose also produce phase shifts in the signals. The introduction of phase shifts in the signals to different ones of the elements, causes the beam position to shift and also undesirably varies the beam pattern. Furthermore, in known antenna arrays of this type, the phase shifts of the signal being fed to the individual elements varies with the degree of attenuation of the signal thereby making more difficult the synthesizing of a particular beam pattern or series of beam patterns.

Still another difficulty, and perhaps the most serious problem experienced in prior arrays of this type, is the loss of gain or reduced efiiciency resulting from changing the beam pattern by the use of variable attenuators. In the usual application, the power being produced by the transmitter during transmission, or the power being received by the antenna array during reception, is gen erally constant. Consenuently, the introduction of attenuating means to control the amplitude of the signals being fed to or received from the antenna elements reduces the power or gain of the antenna whereby variation of the beam-shape and pattern in such attentuating arrangements are made by sacrificing the antenna gain and hence reducing the efficiency of the system.

According to the present invention, there is provided a variable aperture antenna array that permits precise control of the amplitude distribution of signals to the individual ones of antenna elements in such manner that the phase relationship of the signals is maintained relatively constant and the total power being received or transmitted by the array is also maintained constant. Thus, according to the present invention, there is provided a means for precisely varying the antenna beam pattern without undesired phase displacement effects and without appreciable loss in gain or efficiency.

According to preferred embodiments, the amplitude relationship of the signals fed to different elements or segments of the antenna is varied by a novel system of adjustable power divided means which serve to divert the energy in varying ratios to the various antenna elements of the array without appreciably diminishing the total amount of energy being transferred or effecting the im pedance match of the system. Thus, according to the present invention, there is no net sacrifice of energy or power, and the antenna array operates at substantially optimum efiiciency when producing each of a wide variety of different beam patterns or shapes. Furthermore, the construction of the power dividers and the preferred system arrangement are such that the various elements of array are energized in an effective in-phase relation as the amplitudes are varied to achieve differing beam patterns, thereby enabling the antenna aperture to be varied uniformly and progressively, or in other sequences as desired, all with precise control and accuracy.

According to additional features, the invention may be embodied in different systems permitting two dimensional control of the beam pattern by the use of a mattress array of elements, or by the use of secondary apertures such as reflectors. Additionally, the antenna system may be modified to provide polarized beams in one or more geometrical planes as well as other characteristics desired for special application.

It is, accordingly, a further object of the invention to provide a constant power, adjustable beam pattern antenna.

A further object is to provide an adjustable beam pattern antenna having maximum gain and efficiency.

Still another object is to provide such a versatile antenna system that operates over a wide bandwidth of frequencies.

Still another object is to provide such a system wherein the beam-shape may be varied in either one or two dimensions.

Still another object is to provide such a system wherein the beam-shape may be of substantially constant configuration in one dimension and adjustably varied in a second dimension.

Still another object is to provide a constant power antenna system having a variable aperture in two dimen- SlOl'lS.

Still another objects is to provide such a two-dimensional variable aperture antenna system producing differently polarized beams along different axes.

Other objects and many additional advantages will be more readily understood after a consideration of the following specification, taken with the accompanying drawings, wherein:

FIG. 1 is an electrical schematic representation of one antenna ssytem according to the present invention, providing an adjustable beamshape in one dimension;

FIG. 2 is a schematic representation of a preferred power divider means employed in the antenna system of FIG. 1;

FIG. 3 is a diagram similar to FIG. 1 and illustrating a modified antenna array ssytem providing an adjustable beam-shape in one dimension;

FIG. 4 is a block diagram representation of a cruciform antenna array system that may be energized as in FIG. 1 or FIG. 3, or otherwise, and providing adjustment of the beam-shape in two dimensions;

FIGS. 5 and 7 are block diagrams of mattress antenna array systems according to the invention for providing adjustment of the beam-shape in two dimensions;

FIG. 6 is an electrical schematic diagram illustrating an electrical system for energizing the mattress array of FIG. 5;

FIG. 8 is a block diagram representation of a concentric ring antenna array system according to the invention for providing symmetrical adjustment of the beam-shape about its longitudinal axis;

FIG. 9 is a schematic representation of a variable aperture antenna array system according to the invention and employing a reflector or secondary aperture for beam focusing;

FIG. 10 is an antenna system similar to FIG. 8 and employing a differently shaped reflector;

FIG. 11 schematically illustrates a dual feed antenna system having a reflector that is employed for such purposes as monopulse applications;

FIG. 12 schematically illustrates an antenna array systern for providing a plurality of polarized beams whose beam-shapes are adjustable according to the present invention;

FIG. 13 is a schematic representation of a split feed antenna array ssytem for such purposes as monopulse application; and

FIGS. 14 to 16, inclusive, schematically illustrate the synchronous adjustment of a plurality of the potential dividers according to different embodiments of the invention.

Referring now to FIGS. 1 to 3, for a detailed consideration of the invention, there is shown in FIG. 1 an antenna array comprising a plurality of antenna units 10 to 17 inclusive, that may be dipoles, horns, or other known elements with the array being fed by a common input means such as 23, and a plurality of adjustable power divider means, such as 21, 25, 27, and 35, interconnecting the common input 23 with the various antenna elements 1% to 17 of the array in a given arrangement. All of these elements are reversible in nature and consequently, the array may be fed energy from the common source through input 23 or may receive energy from space and feed the energy biackwardly to the common line 23.

As shown, the interconnecting means between the common input or output 23 and the antenna units 10 to 17 is comprised of a corporate feed system consisting of a series of transmission lines and power splits or junctions, whereby the energy at the various junctions is divided and passes upwardly to the different antenna units.

The variable power divider means 21, 25, 27, land 35,

are inserted at a given four of the junctions and each is, accordingly, provided with a pair of output terminals and a common terminal that receives or transmits the sum of the power passing through the two output terminals. According to the present invention, each of the power dividers 21, 25, 27 and 35, is capable of variably apportioning the power at the common terminal thereof in any desired ratio between the two output terminals without appreciable attenuation of the power, and concurrently maintaining the phase of the signals at the two output terminals constant and in relative phase alignment regardless of the power division adjustment. Consequently, at the four junctions where the variable power dividers are inserted, the ratio of energy being transmitted upwardly and leading to the antenna elements or units may be apportioned in any desired ratio to vary the relative amplitudes of the signals energizing the different ones of the antenna units.

Considering the operation of thiis system and presupposing first that it is desired to uniformly illuminate the tire array with equal power being fed to all the antenna units, the power dividers 21, 25, 27, and 35, are first adjusted to equally divide the power received at the input terminal of each between both output terminals. After this adjustment, the power at input 23 is equally divided among the antenna units, and each of the antenna units is energized by an in-phas-e signal of the same amplitude, and at a power that is one-eighth of the input power. Tracing the passage of a signal from input 23 to the antenna elements 10 to 17, the input signal at 23 is divided equally at the first junction and one-half the power passes over line 22 and the other half over line 40. The power over line 22 is again equally divided by power divider 21 with one-fourth of the power passing upwardly over line 20 and, in turn, being equally apportioned in eighths among antenna units 10 and 11, and with the remaining fourth passing upwardly over line 31 and being equally apportioned by means of power divider 25 among antenna units 12 and 13. Thus each of the antenna units 10, I l, 12, and 13, receives signals of the same amplitude as the others and in an in-phase relationship. Similarly, the remaining antenna units 14, 1-5, 16, and 17, are all equally energized in phase with each other and with units 10, 11, 12, and 13, as may be noted by tracing the signal upwardly from line at} in the same manner as discussed above.

Considering a second example where it is desired to illuminate only one-half of the array, the power dividers 21 and 35, in this instance, are initially adjusted to transmit all of the power from the input terminals thereof over output terminals 31 and 34, respectively, and the remaining power dividers 25 and 27 are adjusted to equally apportion the power at the two output terminals thereof. Tracing the signal through the system, the input signal at 23 is again divided equally over transmission lines 22 and 40 and half is directed to the input terminal of power divider 21 and the other half to divider 35. In this case, however, all of the power received by power divider 21 passes over line 31 and is equally apportioned in fourths to antenna units 12 and 13, whereas no power passes to antenna units 1t) and 11. Similarly, in the opposite branch, all of the power through power divider 35 is directed upward o ver line 34 and equally apportioned by divider 27 to antenna units 14 and 15, whereas no power is permitted to pass to antenna units 16 and 17. Thus, in this second example, all of the power from input 23 is equally apportioned among four of the antenna units 1 2, 13, 14, and 15, and the remaining antenna units 10, 11, and 16, 17, of the array, are not energized. Consequently, there is provided a uniformly illuminated antenna array that is one-half the size of the array described in the first example above. Since the width of the beam being radiated or received by a linear array is inversely proportional to the electrical length of the antenna, this half-size antenna array provides a beam that is twice as wide as that provided by uniformly illuminating the complete eight unit array. Consequently, the antenna apert-ure has been decreased by one-half or made to disappear by this amount.

However, despite the fact that the antenna beam Width has been doubled in the second example over the first, the antenna still functions at a high efiiciency since substantially all of the energy or power from the input is being directed to the antenna units in both instances and no appreciable attenuation takes place. More specifically, in the first example, each of the eight energized antenna units to 17 receives one-eighth of the power from the common source 23, and in the second example each of the four energized antenna units 12 to receives one-fourth of the total power. Consequently, the half power beam width doubles after adjustment of the power dividers 21 and 35, neglecting such effects as side lobes and other effects, but the efficiency remains constant.

Continuing this analysis of operation, the power dividesr 25 and 27 may be next adjusted to direct all of the energy received over their input terminals 3 1 and 34 to only one of their output terminal lines 29 and 32, respectively, whereby all of the power from the common input 23 is diverted to only the antenna units 13- and 14 and the remaining antenna units 10 to 12 and 15 to 17 are de-coupled from the common input 23 and receive no power therefrom. With this adjustment, the electrical length of the antenna array is again divided in half and the beam width is accordingly again doubled in width. However, the power being fed to antenna units 13 and 14 is also doubled since each now receives onehalf the power from the common input 23 whereby the half power beamwidth is again doubled but the array continues to function at substantially maximum efficiency. Thus, by means of the system of FIG. 1, there can be obtained a four-toone variation in the beamwidth provided by the array and without change in the efficiency of the antenna. Stated more technically, the four-to-one ratio of beamwidth variation is obtained without substantially changing the radiating efliciency of the antenna.

Since each of the power dividers 21, 25, 27, and 35 is continuously adjustable to apportion the power from its input terminal in any desired ratio among its output terminals, a continuous variation of the beamwidth may be obtained, with the maximum width being obtained when only antenna units 13 and 14 are energized and the minimum width being obtained when all eight of the antenna units are equally energized. Furthermore, either symmetrical or unsymmetrical beams may be obtained by simultaneously varying the power dividers or by individually varying the power dividers. For example, to obtain a symmetrical variation in beamwidth, the power dividers 21 and 35 may be mechanically coupled together by interconnecting their adjustment means 24 and 36, and the dividers 25 and 27 may likewise be coupled by interconnecting adjustment member 26 with member 28, all as shown in FIG. 14. The power divider 21 controls the division of power between the outer antenna units 10, 11 and the inner units 12, 1'3 and the power divider 35 controls the division of power between outer units 16, 17, and inner units 14, 15 respectively, whereby simultaneously adjusting dividers 21 and 35 bring about a symmetrical collapsing or expansion of the beam about the center axis of the array. Independent adjustment of the dividers, on the other hand, variably apportions the energy fedof the left-hand and right-hand portions of the array and, therefore, permits non-symmetrical variation of the beam about the center axis of the array as may be desired.

The antenna systemof FIG. 1 provides an even ratio of adjustment of the beamwidth covering a maximum range of about 4 to 1. By supplying additional antenna units and by amplifying the corporate feed in the same pyramided manner, as shown, a greater even ratio variation of beamwidth may be obtained.

FIG. 3 illustrates a modification of this system to pro vide an odd ratio of beamwidth variation that is obtainable by interconnecting the corporate feed system in a different manner.

Referring to FIG. 3, there is shown, for purposes of example, a series or array of nine antenna units 61 to 69 inclusive, with all being fed from a common input line 77 by means of a corporate feed system including but two power dividers and 80. In this modification, all of the antenna units may be uniformly illuminated by adjusting the power divider 75 to divert two-thirds of its received energy over output terminal 74 and one-third of its received energy over output terminal 76. The energy over output terminal 74 is equally divided among antenna units 61 to 63 and 67 to 69, whereas the lesser energy over line 76 is equally divided among the three central antenna units 64 to 66, whereby all of the units are equally energized and in an in-phase relationship. To expand this beamwidth by an odd ratio of three-to-one, the power divider 75 is adjusted to divert all of the power over output terminal 76 leading to the three antenna units 64 to 66 and permit no power to pass over line 74 to units 61 to 63 or 67 to 69. Consequently, by this adjustment, the electrical length of the array is reduced to one-third of its former length and the beamwidth is increased by a factor of three. To further expand the beamwidth by another odd multiple of three, the second power divider is adjusted to divert all power over output terminal 82, whereby all of the power from the common input 77 is directed to but a single antenna unit 65. This reduces the length of the array to only one dipole or other radiating element, and reduces the length of the array to one-ninth of its original length, thereby increasing the beamwidth by an odd factor of nine. As in the embodiment of FIG. 1, the power dividers 75 and 80 may be adjusted to any intermediate position, thereby enabling a continuous variation of beamwidth over a full range of nine-to-one. By supplying additional antenna units and expanding the corporate feed system in the odd multiple arrangement, as shown, extended odd ratio beamwidth variations may be obtained, as desired. Again, as in the system of FIG. 1, the efficiency of the antenna remains substantially constant for all adjustments, since as the length of the array is reduced to increase the beamwidth, the total power energizing the remaining antenna units remains the same, whereby the power fed to the fewer antenna elements is increased in inverse proportion to the number of units being energized. Also as in the embodiment of FIG. 1, the power dividers may be mechanically coupled together, as shown in FIG. 15, for simultaneous actuation.

Systems of the type disclosed in FIGS. 1 and 3 may efficiently operate over a wide band of frequencies limited only by the frequency characteristics of the individual components, comprising the antenna units, transmission lines, and power dividers. It is well known that many different types of antenna units and transmission lines are available having a two-to-one or even greater frequency bandwidth. A preferred power divider having a frequency bandwidth at least as great as these ratios is schematically illustrated in FIG. 2. As shown, the divider is comprised of a pair of four-terminal 3 db directional coupler devices 52 and 57 that are electrically interconnected by means of a transmission line from junction 53 to junction 49, and by a phase shifter 54 inserted between junction points 55 and 56. An input signal over line 50 is directed to one input terminal of coupler 52 and the other terminal 48 thereof is connected to a matching or balanced load, indicated as a resistor 51. The two output terminals from the divider are taken from the terminals 58 and 59 leading from the second coupler 57. The division of power between the output terminals 58 and 59 is a function of the phase shift provided by phase shifter 54 and consequently by adjusting the phase shift provided by device 54, the power may be apportioned in any desired ratio between these output terminals 58 and 59. Due to the characteristics of this power divider the signals at output terminals 58 and 59 are always maintained in a constant in-phase relationship for wide variations of the phase shifter 54 over an approximate 180 displacement, or in phase opposition for an additional 180 displacement, whereby for any power ratio desired, the outputs may be maintained either in phase or in phase opposition, as desired. The 3 db directional couplers in strip transmission line, and suitable phase shifters 54 are available with frequency bandwidths of more than two-to-one. Consequently, a given antenna system according to the present invention may be operated at any one of a wide range of different frequencies and function in the manner described above.

Another configuration of this power divider that may be employed in the present invention is described in an article by W. L. Teeter et al., entitled: A Variable-Ratio Microwave Power Divider and Multiplexer, IRE Transactions on Microwave Theory and Techniques, October 1957, pages 227 to 229.

In the antenna arrays of FIGS. 1 and 3, each system produces a fan-shaped beam whose dimensions in one plane (such as elevation), are substantially fixed and whose dimensions in the other, or azimuth plane, are variable with adjustment of the power dividers. When control of the beam-width in both azimuth and elevation is desired, a pair of such arrays, such as 88 and 89 in FIG. 4, may be provided and arranged at right angles to each other. As generally shown in block diagram form in FIG. 4, each of the arrays comprises a linear series of antenna units with the units 90 to 96 of array 88 being disposed along a vertical axis and the units 97 to 103 of array 89 being disposed along a horizontal axis. The signals fed to the units of each array are controlled by power dividers in the arrangement of either FIG. 1 or FIG. 3, and consequently this generally cruciformshaped arrangement provides an independent adjustment of the beam along both horizontal and vertical axes.

Where a more complete control of the beamwidth and shape in both the horizontal and vertical planes is desired, a mattress array, as generally indicated in FIG. 5, may be employed. In this arrangement, a series of horizontal linear arrays, such as the seven unit horizontal arrays numbered 164 to 110 are stacked one above the other to form the mattress or two-dimensional rectangular array, as shown. Each of the layers or horizontal linear arrays may comprise as many antenna units as desired with the units in each array being energized in common from a single input by means of the power dividers and corporate feed arrangements of FIG. 1 or FIG. 3, depending on the odd or even ratios desired. The common input to each horizontal layer is, in turn, interconnected by a master corporate feed system including additional power dividers, whereby the complete mattress may receive from or transmit energy to a single master input line.

FIG. 6 schematically illustrates one preferred corporate feed system for the mattress array of FIG. 5. As shown, the upper horizontal linear array or layer 164 is comprised of seven antenna units 104a to 104g, inclusive, that are interconnected with a common input line 111, by a corporate feed system similar to FIG. 3, and including three power dividers 112, 113, and 114. In a similar manner, each of the other horizontal layers is also comprised of seven antenna units disposed along a horizontal axis with each having a common input line 115 to 120, inclusive, and three power dividers making a total of twenty-one power dividers for controlling the horizontal beam-shape provided by the mattress.

For controlling the vertical beam-shape of the mattress, the seven input lines 111 and 115 to 120 are, in turn, interconnected to a master input line 121 by means of a corporate feed system including three additional power dividers 122, 123, and 124, thereby to control the relative power being directed to the different horizontal layer arrays.

In operation, adjustment of the three power dividers 122, 123, and 124, controls the vertical beam-shape of the pattern produced by the mattress and the adjustment of the power dividers in each horizontal layer such as dividers 112, 113, and 114, in upper layer 104 controls the horizontal beamwidth of each layer. By interconnecting or gauging the corresponding power dividers in the different horizontal layers for simultaneous adjustment, as shown in FIG. 16, only three separate adjustments are required for controlling the horizontal beamshape of the mattress. Similarly, the power dividers 122, 123, and 124 may also be ganged together, as shown in FIG. 16, to provide simultaneous adjustment thereof. It is also contemplated that gearing, cams, or other interconnecting means may be employed in the actuators to mechanically couple the power dividers in any given ratio or arrangement to provide sequential or simultaneous variation of the mattress beam-shape in any desired manner.

By eliminating certain of the corner antenna units from the mattress array of FIG. 5, such as units 1194a, 1104b, 164- 104g, a, 105g, 1119a, 169g, 1110a, 11912, and 110g (illustrated in lined form in FIG. 5), a pseudoelliptical aperture is obtained that decreases the gain of the antenna slightly but provides better side lobe levels. This variation also simplifies the antenna construction by eliminating certain of the power dividers and transmission lines and junctions as well as obviously reducing the number of antenna units.

A mattress array similar to PEG. 5 may be employed for providing phase or amplitude monopulse information. One such configuration is illustrated by the block diagram schematic drawing of FIG. 7. As shown, the upper vertical half of this split-type mattress may comprise four horizontal linear rows or layers 126 to 129, inclusive, with each layer containing eight antenna units, and the lower half may likewise be comprised of four layers 130 to 133, or rows with eight antenna elements in each. This system is also symmetrical about the vertical axis and would be fed by a corporate feed system similar to FIG. 1. Considering each half of this mattress as a separate array as in FIG. 5, a corporate feed system including a total of forty power dividers (not shown) enables phase or amplitude monopulse in either the azimuth or elevation planes. By eliminating the individual antenna units at the corners of the mattress, as illustrated by the lined blocks, the number of power dividers may be reduced to thirty-two.

A further modification for providing a pencil-like beam that is adjustable in width about two dimensions is shown in FIG. 8. In the embodiment, the individual antenna elements are in the form of a plurality of concentrically arranged ring-shaped antennae 137 to 142, inclusive, of progressively increasing diameter about a central substantially circularly-shaped element 136. All of the rings and the central antenna element 136 are interconnected by a corporate feed system of the odd multiple type similar to that shown in FIG. 3 and including three power dividers 143, 144-, and 145 in cascade leading from the common input line 146. Since the ring-shaped antenna elements provide a generally pencil-shaped beam, adjustment of the three power dividers 143, 144, 145, in sequence decreases the power distribution symmetrically from the outer ring antenna 142 toward the inner element 136, or the reverse to progressively increase or decrease the diameter of the pencil beam being produced, thereby to provide a variable beamwidth in two dimensions. A greater or lesser number of such ring antenna elements may, of course, be provided for varying applications, in either odd or even multiplies, and the corporate feed system may likewise be in the even multiple configuration of FIG. 1 or the odd multiple configuration of FIG. 3, as desired.

Another manner of providing variation of the beam width in one dimension while shaping the beam in a sec 9 nd dmension is by employing a single linear antenna array of the type show in FIG. 1 or FIG. 3, together with a secondary aperture such as a reflector. One such arrangement is illustrated in FIG. 9, wherein a single linear array of antenna elements 148 is employed with a cylindrically-shaped parabaloid reflector 149. The array 148 may be of the configuration of FIGS. 1 or 3, and consequently all of the antenna elements may be uniformly illuminated or the distribution of power to the individual units apportioned in any desired ratio. With all elements uniformly illuminated the antenna produces the narrowest pencil-shaped pattern, generally as indicated at 150 and having a pseudo circular cross section as indicated at 151, whereas with only one of the elements 148a being illuminated, the pattern is expanded to the shape indicated at 152 having an elliptically-shaped cross section 153. This antenna configuration finds utility as the antenna system for a collapsible beam nodding height finder radar but is, of course, also useful in many other applications.

FIG. illustrates a modification somewhat similar to FIG. 9 for the purpose of providing a differently shaped beam in the vertical direction or elevation and a variable beamwidth in the horizontal direction or in azimuth. As shown, the linear array 155 energized according to FIG. 1 or FIG. 3, is disposed along a horizontal axis and the reflector, generally indicated at 156, is provided with a shaped surface to provide a cosecant square-shaped beam in elevation. In this case, adjustment of the power dividers (not shown in FIG. 10) variably apportions the power among the antenna elements of the array 155 to vary the beamwidth in the azimuth direction, but the shape of the beam in elevation remains fixed as determined by the shaped reflector surface 156. Obviously, many differently shaped reflectors can be employed to provide a wide variety of fixed beam shapes along one dimension while the beamwidth in the other dimension is variable according to adjustment of the power dividers.

An extremely versatile antenna array system is shown in FIG. 11 employing a pair of linear arrays 158 and 159, each of the general type as in FIG. 1 or FIG. 3, and a cylindrical parabola reflector 160, as in FIG. 9. The two inputs (not shown) leading one to the upper array 158 and the other to the lower array 159 may be employed for phase type monopulse comparison or suit-ably connected in a system for broadband amplitude monopulse application. More specifically, with this arrangement beamwidth variation in one plane may be achieved with amplitude monopulse in both planes or in two dimensions. Since most of the problems required of a variable radar system may be solved by a combination of search and tracking antenna having variable beamwidth in the elevation plane, a system employing the antenna system of FIG. 11 is capable of achieving most modes of operation required of a three dimensional radar system.

Where it is desired to provide polarized beams in more than one geometric plane, a plurality of arrays in the cruciform type configuration of FIG. 4, or other configurations disclosed, may be employed by providing differently polarized antenna units in the different arrays. A more efiicient system of this type is shown in FIG. 12.

In the embodiment of FIG. 12, two quadrature polarized antenna arrays '165 and 166 are arranged in cruciform-shape and are arranged to feed a pair of intermeshed cylindrical paraboidal reflectors 167 and 168. The intermeshed reflectors 167 and 168 are each comprised of parallel grids or rods, with the parallel cylindrically-shaped grids of reflector 1167 being at right angles to the parallel cylindrically-shaped grids of reflector T68. Consequently, the grids of reflector 167 are transparent to a beam polarized at right angles thereto, but will reflect a beam polarized in the same direction and the grids of reflector .168 will reflect the polarized beam passing through grid 167, but will be transparent to the polarized beam reflected by the grids of 167. Thus, this arrange- 10 ment permits simultaneous operation of both arrays with diflerent polarizations. A wide variety of complex polarizations are thus obtainable with this construction.

The various modifications, as described above, may be generally classified for discussion purposes as being symmetrical arrays having variable beamwidth control since each system possesses at least one antenna array having a symmetrically arranged corporate feed system. A pair of such arrays or a pair of such mattress arrays may be employed for monopulse tracking applications, as described in the embodiment of FIG. 7 and FIG. 1 1.

According to another embodiment of the invention, there is provided an antenna array system of this type providing a variable beamwidth control that may be classified as being a mono-symmetrical array or split aperture array wherein the corporate feed system does not symmetrically interconnect the antenna elements to a common input line.

FIG. 13 illustrates a pair of such unsymmetrical arrays and 171 in side-by-side, mirror image arrangement about a central axis 172, which arrangement is particularly adapted for use in monopulse applications.

As shown in FIG. 13, this system, which may be termed a split aperture array, is comprised of a left-hand section of four antenna units 170a to 170d interconnected by a corporate feed system including two power dividers 173 and 174 to a common input line 175; and a righthand section of four antenna units 171a to 17111 similarly interconnected to a common input line 178. The common lines 175 and 178, leading to the left and right hand arrays are, in turn, suitably coupled through junctions, switches, or other transmission means 179 and 180 to a master input line 181, whereby power may be transmitted from or to both arrays 170 and 171 to the master input 181.

The operation of each array 170 and 171 is generally the same as in FIG. 1 or FIG. 3, and the width of the beam being produced thereby is controlled by the power dividers feeding that array. However, since the two arrays are displaced from one another, the beam being produced by each is likewise displaced in space from that of the other, whereby this split aperture system may be employed for phase type monopulse comparison purposes or for broadband amplitude monopulse use by employing the two common output lines 175 and 178. The functioning of this system is substantially the same as described above, and this split aperture arrangement may be employed in the reflector systems as describe-d above as well as in the mattress antenna systems as described.

The embodiments described above are not to be considered as limiting the entire range of antenna configurations according to the present invention, but on the contrary serving only to illustrate details of certain preferred constructions. ments is each array is limited only by other considerations including the size and complexity of the system and corporate feed system, the number of adjustments desired, and the like.

Various other types and configurations of the antenna elements themselves in either linear or other type arrays are, of course, contemplated, as are other kinds and variously shaped secondary apertures or reflector means. The corporate feed systems for the arrays may be either symmetrical or unsymmetrical and may be con-- structed to provide either even or odd ratio of adjustment, as in FIG. 1 or FIG. 3. Since these, and other variations may be made by those skilled in the art without departing from the scope of the invention, this invention should be considered as being limited only by the claims appended hereto.

I claim:

'1. A variable aperture constant power antenna comprising a plurality of indivirual antenna units spaced apart from one another and means coupling energy to and from said units, said coupling means including at For example, the number of antenna ele-' least one variable power divider means having an input line to receive and transmit energy and a pair of output lines that each receive and transmit a variable portion of the energy from said input line and together transmit and receive substantially all the energy transferred from and to said input, each of said output lines being coupled to different preselected ones of said antenna elements, said power divider means being variable to apportion the total power transferred by said power divider means among preselected antenna units to vary the aperture of the antenna array without diminishing the power transfer thereto and therefrom, or effecting the impedance.

2. In the antenna array of claim 1, a plurality of said power divider means being connected in cascade in said coupling means with an output line from a first of said power dividers being connected to the input line of a second of said power dividers.

3. In the antenna array of claim 2, the second output line of said first power divider being connected to a preselected individual antenna unit and the second output line of said second power divider being connected to another preselected individual antenna unit.

4. A scale-of-two variable aperture contsant power antenna array comprising a pair of antenna units, an adjustable power divider having an input terminal and a pair of output terminals with the total power received and transmitted over the input terminal being variably divided between the output terminals substantially without attenuation thereof, means connecting one of said output terminals to one of said antenna units and the other of said output terminals to the other of said antenna units whereby all of the energy transferred by said input terminal may be selectively transferred to either of the antenna units or divided between said units in any desired ratio.

5. A scale-of-three variable aperture antenna array including three antenna units, a variable power divider having an input and a pair of outputs with the total power received and transmitted over the input being variably divided between the output lines substantially without attenuation thereof, means connecting one of said output terminals to one of said antenna units and the other of said output terminals in common with a pair of antenna units, whereby substantially all of the energy transferred by said input line may be selectively transf-erred to either said one antenna unit, said commonly connected pair of units, or divided therebetween in any desired ratio.

6. A variable aperture antenna comprising an array of antenna units, power dividing means for selectively receiving from and transmitting energy to said units, said power dividing means being adjustable to variable apportion the energy among said units without appreciable attenuation of said energy and while maintaining the phase substantially constant, thereby to vary the beam pattern produced by the array by varying the amplitude distribution of the energy among the antenna units.

7. A variable beamwidth mattress antenna array comprising: a plurality of linear antenna arrays, each being comprised of a plurality of antenna elements; power divider means for each linear array for variably apportioning all of the power from and to a common input-output means associated with each linear array among the different elements of that linear array, a master input-output means coupled to the common input-output means from all of the linear arrays, said coupling means including additional power divider means for variably apportioning the power among the different linear arrays in desired proportions, said power dividers each having a single input and a pair of outputs and being adjustable to variably apportion substantially all of the energy transferred from and to said input among said outputs in desired ratios Without attenuation of the power and while maintaining the impedance at each of the inputs and outputs substantially constant for all adjustments.

8. In the mattress array of claim 7, interconnecting means for commonly connecting given power dividers from different ones of said linear arrays for simultaneous adjustment.

9. A variable beamwidth polarized antenna array comprising a plurality of antenna units and a corporate feed means for commonly connecting all of said units with a common polarized input-output means, said corporate feed means including a plurality of power dividers, each having three terminals and being adjustable to variably apportion all of the power from and to said first terminal in desired ratios among said second and third terminals without attenuation of said power and while maintaining constant the phase at said second and third terminals during wide range adjustment of the power divider.

10. A plurality of antenna arrays as in claim 9, each being angularly displaced from the others.

11. In the antenna array of claim 10, polarized reflector means for each different one of the antenna arrays, with each reflector means being transparent to the polar ized beam-s of all arrays excepting for its associated array.

12. in the antenna array of claim '11, said reflector means comprised of a plurality of intermeshed parallel grid reflectors, with a different parallel grid reflector for each array and with each of said reflectors being angularly oriented in the plane of the polarized beam produced by its associated array.

13. A split aperture adjustable beamwidth antenna comprising a first and second even series of antenna elements; adjustable power divider means for each series of elements and being asymmetrically connected thereto to variably apportion the power among the elements in progression from one end of each series to the other, and means supporting said two series in side-by-side relation on opposite sides of a common axis, whereby the beams provided by said two series may be displaced and symmetrical about said common axis, and means connecting said power divider means from both series for selectively enabling common transmission and comparison of the signals received.

14. A variable beam pattern antenna array comprising a plurality of individual antenna units spaced apart from one another, a common terminal for transferring energy to and receiving energy from said array, means for variably energizing said ditferent units of the array in an inphase relationship with different amplitude signals to vary the beam pattern of the array, said means comprising a pyramid corporate feed system having a plurality of branching junctions interconnecting the individual units with the common terminal, each junction having an input channel and a plurality of output channels with the total energy transferred by the output channels substantially equaling the energy from the input channel and with the energy in the output channels being in an in-phase relationship, a variable power divider being provided at one of the junctions, and means for adjusting said power divider to variably apportion the ratio of energy at the output channels of that junction while maintaining the phase relationship at said output channels substantially constant.

15. A variable beam pattern antenna array comprising a plurality of individually energizable antenna units, a common terminal, and a parallel feed system interconnecting said common terminal with each of said antenna units, said parallel feed system including a plurality of separate channels for directly coupling said common terminal with different ones of said units, adjustable power divider means interconnecting said channels for variably apportioning the energy among said channels without substantial attenuation of the energy and while maintaining the phase relationship of the energy in the channels substantially constant over the range of adjustment, and means for adjusting said power divider means to vary the antenna beam pattern.

16, I an antenna array comprised of a plurality of antenna units spaced apart from one another, and a common input-output means for transmitting and receiving energy from said array, adjustable means for varying the relative amplitude of the energy transferred from said common means to various of said antenna units without appreciable attenuation of the total energy transferred between all of said units and said common means, said amplitude varying means including a power divider having a single input and a pair of outputs and being adjustable to variably apportion the energy being transferred by said input among said outputs without appreciable attenuation of said energy, a plurality of said power divider means being oonnected in cascade with the input of one of said power divider means being connected to one of the outputs of another of said power divider means, and

at least one pair of said power divider means being conneeted for simultaneous adjustment.

17. In an antenna array comprised of a plurality of antenna units spaced apart from one another, and a common input-ouput means for transmitting and receiving energy from said array, adjustable means for varying the relative amplitude of the energy transferred from said common means to various of said antenna units without appreciable attenuation of the total energy transferred between all of said units and said common means, said amplitude varying means including a power divider having a single input and pair of outputs and being adjustable to variably apportion the energy being transferred by said input among said outputs without appreciable attenuation of said energy, a plurality of said antenna arrays all receiving and transmitting energy from and to a master input-output means, each of said arrays having a common input-output means and being connected thereto by power divider means to variably apportion the energy from said common means among the individual antenna units, and additional power divider means interconnecting the plurality of common means from said different antenna arrays with said master input-output means to variably apportion the energy from and to said master input-output means among the different antenna 4 arrays.

18. In an antenna array comprised of a plurality of antenna units spaced apart from one another, and a common input-output means for transmitting and receiving energy from said array, adjustable means for varying the relative amplitude of the energy transferred from said common means to various of said antenna units without appreciable attentuation of the total energy transferred between all of said units and said common means, said amplitude varying means including a power divider having a single input and a pair of outputs and being adjustable to variably apportion the energy being transferred by said input among said outputs without appreoiable attenuation of said energy, and said antenna units comprising a plurality of concentrically positioned arcuately shaped radiating and receiving elements.

19. In an antenna array comprised of a plurality of antenna units spaced apart from one another, and a common input-output means for transmitting and receiving energy from said array, adjustable means for varying the relative amplitude of the energy transferred from said common means to various of said antenna units without appreciable attenuation of the total energy transferred between all of said units and said common means, said amplitude varying means including a power divider having a single input and a pair of outputs and being adjustable to variably apportion the energy being transferred by said input among said outputs without appreciable attenuation of said energy, and the addition of a secondary beam focusing means for shaping the beam.

References Cited by the Examiner UNITED STATES PATENTS 0 CHESTER L. JUSTUS, Primary Examiner. FREDERICK M. STRADER, Examiner.

W. S. PYLES, A. E. HALL, H. C. WAM-SLEY,

Assistant Examiners. 

6. A VARIABLE APERTURE ANTENNA COMPRISING AN ARRAY OF ANTENNA UNITS, POWER DIVIDING MEANS FOR SELECTIVELY RECEIVING FROM AND TRANSMITTING ENERGY TO SAID UNITS, SAID POWER DIVIDING MEANS BEING ADJUSTABLE TO VARIABLE APPORTION THE ENERGY AND WHILE MAINTAINING THE ATTENUATION OF SAID ENERGY AND WHILE MAINTAINING THE PHASE SUBSTANTIALLY CONSTANT, THEREBY TO VARY THE BEAM PATTERN PRODUCED BY THE ARRAY BY VARYING THE AMPLITUDE DISTRIBUTION OF THE ENERGY AMONG THE ANTENNA UNITS. 